What
A hook is a script or plugin step that runs at a set point, here when you submit a prompt. When such a hook rewrites your prompt, Claude Code now puts the new text into your actual message, whether it is plain text or made of several parts. Before, the rewrite could land on the wrong object, leaving Claude to see the prompt as you typed it.
Why
Hooks that change or add to your prompt should now have their changes seen by Claude.
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
It is not certain the old behaviour was actually broken in practice.